Oscillator



Jan. 15, 1935.

H. o. PETERSON ET AL 1,987,867

050 ILLATOR Filed June 8, 1951 FM P4 I M00044 70R BUFFER AMPL IF/EE FIRST seen/v0 05 7567a? 0575:: me

INVENTORS HAROLD 0. PETERSON De WITT R. GODDARD ATTORNEY Patented Jan. 15, 1935 I I V UNITED STATES PATENT OFFICE OSCILLATOR Harold Olaf Peterson and De Witt Rugg Goddard, Riverhead, N. Y., assignors to Radio Corporation of America, a corporation of Delaware Application June 8, 1931, Serial No. 542,796'

6 Claims. (01. 250-36) This invention relates to an oscillator and in It is a further object of our present invention particular to oscillators of the electron discharge to so proportion the inductance or choke coil so device type. v v used in parallel with the crystal that the coil Heretofore, electromechanical resonators or together with the capacity of the tube and crysotherfrequency stabilizing devices have been aptal holder or crystal electrodes, will resonate at a plied, when applied to electron discharge devices, frequency less than, or, more specifically, from only to such devices wherein feed back tool; place 50% to 80% of that at which the crystal confor the generation of high frequency oscillations. trolled oscillator operates. However, it is to be Bro-adly,it is an object of our present invention noted that successful operation is not limited to 10 to provide for the electromechanical frequency these values, which are preferred inasmuch as 10 control of electron discharge device oscillators from actual practice it has been discovered that other than the regeneratively coupled or conthose values result in most successful operation of nected type. the oscillator.

For example, oscillations have been produced Itis a further object of our present invention 35 with an electron discharge device having an anto provide a dynatron oscillation generator utilizode a cathode and a control electrode, by maining an electron discharge device having more than taining the control electrode at a positive pothree electrodes. That is, it is an object of our tential relative to the unidirectional potential invention to provide an electron discharge device of the anode and cathode. For various reasons, oscillator as described hereinabove wherein an however, the frequency of oscillations generated additional electrode is provided adjacent the cath- 20 in this manner is not sufficiently constant, and, a ode for controlling the emission of electrons, further object of our present invention is to proand/or one or more additional control electrodes vide in combination with an electron discharge are provided as found desirable. device oscillator the type just described, a piezo- As required by law we have defined our inven- 5 electric crystal or electromechanical vibrator for tion with particularity in the appended claims. controlling the frequency of oscillations so gen- However, it may best be understood both as to its erated. structural organization and mode of operation by Still a further object of our present invention is referring to the accompanying drawing, wherein, to apply piezo-electric crystal control to a dyna- Figure 1 illustrates, according to our present tron oscillator. Such an oscillator usually takes invention, a crystal controlled electron discharge 30 the form of an electron discharge devicehaving device oscillator wherein an electrode intermedian anode a cathode and a grid wherein the grid ate the anode and cathode of the device is mainis maintained at a positive potential relative to tained at a positive potential relative to the anthe anode and cathode such thatthe device has odeand cathode, a 5 a negative resistance characteristic. According- Figure 2 illustrates a modified form of'ourimly, when the negative resistance of the device proved oscillation generator as applied to a heteris less than L-z-RC' where R is the resistance of odyne receiver, and, a tuned circuit associated with the device at the Figure 3 illustrates, according to our present frequency of oscillation and L and 0 indicate invention, an improved oscillation generator uti-- respectively values of the inductive and capacitive lizingan electron discharge device of the pentode 40 elements of the tuned circuit, oscillationswill be or five electrode type. Set D- Turning to Figure 1, the control electrode 2,

According to our present invention, circuits or inv other words, the grid or electrode interare provided whereby a piezo-electric crystal remediate the anode 4 and cathode 6 of' electron places the ordinary tuned circuit heretofore used discharge device 8 is maintained at a positive 45 in connection with a dynatron oscillator whereby potential relative to the anode and electron frequency stability is materially enhanced. emitting cathode by connecting it through con- 'Inasmuch as the crystal would prevent the ductor 10 to a sourceof unidirectional potential application of unidirectional potentials to at e Shown in the form Of a battery least one of the electrodes to which it is connected, Accordingly, the electron discharge device will an impedance, preferably in the form of a choke have a negative resistance characteristic such coil is used, according to our present invention, that by virtue of this characteristic oscillations to shunt the crystal whereby unidirectional pomaybe generated. To cause such generationlof tential may be applied to the electrode otherwise Oscillations, e n a ode 4 and cathode isolated for unidirectional potentials, 6 we connect an electromechanical resonator 55 here shown in the form of a piezo-electric crystal 14 shunted by the series combination of a choke coil 16 and resistance 18. Anode potential is supplied from source 12 through tapping lead 20 through the series combination of choke 16 and resistance 18 to the anode; and, in order to prevent short circuiting of the anode supply source, ablocking condenser 22 offering little impedance to high frequency currents is connected between the cathode and the shunt combination of choke 16, resistance 18 and crystal 14. We have found that by proportioning the inductance 16 such that it, together with the interelectrode capacity of crystal 14 and the capacity of the electron discharge device 8, resonates at a frequency less than and preferably from to 80% of frequencies from the oscillations generated by the electron discharge device oscillator, most satisfactory operation of the oscillator will be obtained. However, it is to be clearly understood that oscillations can be produced without such a choice of value for inductance coil 16.

Moreover, it is to be understood that simply a choke coil rather than the series combination of choke and resistance 18 may be used, or in other words, any conductive impedance may be connected between the anode source and the anode in order to prevent the crystal from isolating the anode for unidirectional polarizing potential.

Output energy may be fed, as indicated, to a buffer amplifier 24 in turn supplying energy, if desired, to a frequency multiplier 26. The frequency multiplied energy may be modulated in 7 any suitable fashion by a modulator 28 whose output is amplified to a suitable radiating value by a power amplifier 30 before radiation over antenna 32.

The present invention may be applied equally as well to electron discharge devices of the screen grid or four electrode type and devices of the pentode or five electrode type. Thus, as shown in Figure 2, electron discharge device 8 is of the screen grid type wherein the screen grid 34, or in other words, the grid adjacent the anode 4 and intermediate the grid 36 adjacent the cathode and the anode, is maintained at a positive potential by tapping it on to potentiometer 38 such that device 8 has a negative resistance characteristic. The control electrode 34 as shown is grounded for radio frequency currents by the action of by-passing condenser 40.

Grid 36 or electrode 36 adjacent the cathode 6 is maintained at a small positive potential by the action of a source of potential here shown in the form of a battery 42 whereby better control of electron emissivity of the cathode may be obtained.

Anode potential is supplied through potentiometer 44 and impedance 46 preferably in the form of a choke coil shunting the frequency controlling crystal or electromechanical resonator 14. As illustrated, impedance 46 is grounded at an end away from the electrode to which it supplies unidirectional potential, for radio frequency currents by the action of by-passing or blocking condenser 48 whereby flow of radio frequency currents through the supply source is prevented. Wide frequency changes may be obtained by changing the crystal 14, and, small changes in frequency may be obtained by varying the interelectrode spacing of the electrodes for the c ystal.

The oscillation generator illustrated in Figure 2 is shown in combination with a superheterodyne receiver. Output energy from the crystal controlled oscillator is fed to a buffer amplifier 24 in turn supplying energy to a first detector 50. The first detector is also supplied with energy from a radio frequency amplifier 52 coupled in turn to a radio frequency collecting antenna 54. The output of the first detector may then be fed to an amplifier if desired and then to a second detector 56 in turn actuating a translating device such as ear phones 58.

In the arrangement shown in Figure 3 the piezo-electric crystal 14 is used to control the frequency of oscillation of a pentode electron discharge device 8. As illustrated, the grid or control electrode 34 adjacent the anode and the grid or control electrode 36 adjacent the cathode are fed with unidirectional potentials from potentiometer-s 60, 62 respectively connected to the source of anode potential as indicated. The control electrode or grid 64 intermediate the grids 34, 36 is polarized suitably to a suitable value by a source of potential here indicated in the form of battery 66. Anode potential is supplied from potentiometer 68 through milliameter '70 and impedance 72 preferably in the form of a choke coil of such inductive value that it, together with the interelectrode capacity of crystal l4 and the interelectrode capacity of electron discharge device 8 resonates at a frequency from 50% to 80% of that of the frequency of oscillations generated 1 by the electron discharge device 8.

A point on impedance '72 away from the point connected to the anode of device 8 is grounded for radio frequency potentials by the action of by-passing and blocking condenser 74. Of course,

each of the electrodes is so polarized that the device 8 has a negative resistance characteristic suitable for the production of high frequency oscillations when crystal 14 is placed into circuit. By the use of electrodes 64 a still finer control of electron emissivity may be obtained and hence more stable generation of oscillations. Output energy may be taken from conductors 73 to any suitable utilization circuit.

Various changes will, of course, readily suggest themselves to those skilled in the art. Thus, the piezo-electric crystal may be replaced by a magnetostriction oscillator usually in the form of a bar of magnetic material of suitable dimensions surrounded by a high frequency coil. Consequently, when replacing the crystal shown in Figure l the choke 16 may be replaced by the coil of the magnetostriction oscillator. Similarly, when substituting this type of oscillator for the crystal in Figures 2 and 3, the crystal may be omitted, and, the coil of the magnetostriction oscillator made to replace the choke coils 46 and 72 respectively.

Consequently, the present invention is not to be limited in scope by the exact circuits illustrated but is to be given a scope fully commensurate with that of the appended claims.

Having thus described our invention, what we claim is:

1. An electron discharge device oscillator comprising an electron discharge device having an anode a cathode and a control electrode, means for polarizing the electrodes of said electron discharge device, a piezo-electric crystal resonator coupled to electrodes of said electron discharge device, and, a choke coil effectively in shunt with said piezo-electric crystal, the inductance of the coil together with the capacity of the electrodes of said crystal and the interelectrode capacity of said electron discharge device being such as to resonate at a frequency substantially less than the frequency at which said crystal is caused to operate. i

2. An electron discharge device oscillator comprising an electron discharge device having an anode a cathode and a control electrode, means for polarizing the electrodes of said device, a piezo-electric crystal for controlling the frequency of oscillations generated by said device, said piezo-electric crystal being connected between a plurality of electrodes of said device, a choke coil for supplying unidirectional potential to one of the electrodes to which said piezo-electric crystal is connected, the inductance of the choke coil together with the capacity of the electron discharge device and the electrodes of said crystal being such as to resonate at a frequency from 50% to 80% of the frequency of oscillations generated by said electron discharge device oscillator.

3. An o'scillation generator comprising an electron discharge device having an anode a cathode, a grid adjacent said cathode, a grid adjacent said anode, and a grid intermediate said grids, means for polarizing said grids whereby said electron discharge device has a negative resistance characteristic, a piezo-electric crystal, low impedance connections connecting said crystal to said anode and cathode, an impedance connected to said anode, means for supplying unidirectional potential through said impedance to said anode, and, means for grounding for high frequency currents, a point on said impedance away from the point connected to said anode, the inductance of said impedance, together with the capacity of said electron discharge device and the inter-electrode capacity of said piezo-electric crystal, resonating at a frequency from 50% to 80% of the frequency of oscillations generated by said electron discharge device.

4. In apparatus of the character described, an electron discharge device having within an hermetically sealed container, an electron emitting cathode, an anode, and a grid structure intermediate said anode and cathode, a piez'o-electric crystal connected to two of the electrodes of said electron discharge device for starting and maintaining oscillation generation by said device at a frequency corresponding to a natural frequency of said crystal, and, a circuit efiectively in shunt with said crystal for establishing a unidirectional current path to an electrode of said device to which said crystal is connected, said circuit in combination with the capacities associated with said piezo-electric crystal being of such a value in impedance as to resonate at a frequency substantially lower than the frequency of oscillation of said crystal.

5. In apparatus of the character described, an electron discharge device having within an hermetically sealed container, an electron emitting cathode, an anode, and a grid structure intermediate said anode and cathode, a piezo-electric crystal connected to two of the electrodes of said electron discharge device for starting and maintaining oscillation generation by said device at a frequency corresponding to a natural frequency of said crystal, and, a circuit effectively in shunt with said crystal for establishing a unidirectional current path to an electrode of said device to which said crystal is connected, said circuit in combination with the capacities associated with said piezo-electric crystal being of such a value in impedance as to resonate at a frequency from 50 to 80 percent of the frequency of oscillation of said piezo-electric crystal.

6. oscillatory apparatus comprising an electron discharge device having within an evacuated container an anode an electron emitting cathode and an electrode intermediate said anode and cathode, means for polarizing said intermediate electrode to a positive potential relative to said cathode, means to polarize said anode to a lesser positive potential with respect to said cathode, an electromechanical resonator, connections connecting said electromechanical resonator to two of said electrodes for starting and maintaining generation of oscillations at a frequency corresponding to a frequency of said electromechanical resonator, the inductance of said connections together With the electrical characteristics of said resonator and the interelectrode capacity of said device being such as to resonate at a frequency substantially less than the frequency at which said resonator vibrates.

HAROLD OLAF PETERSON. DE WITT RUGG GODDARD.

DISCLAIMER 1,987,867 .-Ha10ld Olaf Peterson and De Witt Rugg Goddard, Riverhead, N. Y. OSCILLATOR. Patent dated January 15, 1935. Disclaimer filed July 1, 1938, by the assignee, Radio Corporation of America. Hereby enters this disclaimer to claims 2 and 5 of said Letters Patent.

[Ofiioial Gazette August 2, 1938.] 

